This kind of oil-in-water type emulsions have widely been used for manufacturing toilet articles, foods, paints, and chemical products, as well as photographic light-sensitive articles.
In the photographic light-sensitive articles, for example, an emulsified material has been prepared in such a manner that an oil-soluble material such as a color image forming compound that is so-called a coupler, a diffusion-transfer compound, a color-fogging preventive, a color-fading preventive, a color-mixing preventive, a UV-absorbent, or a color-thickening agent, is dispersed in an aqueous solution of a high-molecular substance such as gelatin. Such oil-in-water type emulsified materials comprising the above-given oil-soluble materials have usually been prepared in the following manner. First, an oil-phase solution is prepared by dissolving an oil-soluble material in an organic solvent. The resulting oil-phase solution is then added onto the liquid-level of a aqueous-phase solution containing a water-soluble high-molecular substance, by making use of an emulsifying aid if required, and is then so dispersed as to be emulsified. In this way, an oil-soluble material-containing oil-in-water type emulsified material having an average grain-size of approximately 0.1 to 1.0 .mu.m may be prepared.
The solvents such as ethyl acetate each having a boiling point lower than that of water, which have been used often in such a process as described above, will become unnecessary after the time when the dispersion is completed. In many cases, therefore, such solvents are removed from an emulsifying tank by reducing the air-pressure in the tank by means of a vacuum pump connected to the tank.
When producing photographic light-sensitive articles, an emulsified dispersion liquid often shows a behavior of forming bubbles.
The emulsifying tank is therefore filled with bubbles so as not to smoothly remove the solvents, because the bubbles will reduce the evaporative surface areas and, along therewith, the bubbles will invade inside the exhaust pipe when the solvents are to be removed by reducing the air-pressure in the tank, so that a big loss may be caused and the exhaust pipe should be cleaned every time when completing an emulsification-dispersion step.
There have been well-known methods of eliminating the production of bubbles, namely; &lt;1&gt; a method in which a rotary blade which is the so-called bubble-breaker is to be provided inside a liquid tank or exhaust pipe; &lt;2&gt; another method in which a tank capacity is to be made far larger relatively to the amount of processing solution to be used; and &lt;3&gt; a further method in which a debubbling agent is to be used.
However, in method &lt;1&gt;, the bubbles adhering to the rotary blade should be cleaned up in due course, and such cleaning requires a lot of trouble. In method &lt;2&gt;, not only the installation space and facility cost will be increased, but also the bubbles adhering to the tank will be a loss. And, in method &lt;3&gt;, there are still problems remaining unsolved, such as a bad influence exerted, by mixing a debubbling agent into emulsions, on the characteristics of the emulsified materials including particularly those for photographic light-sensitive articles which require strict quality.